A 1/34th scale model of what the Crazy Horse sculpture will look like, foreground, frames the actual carving in 2006.

M. Spencer Green AP

South Dakota is famously home to Mount Rushmore, but it's also been making room for a second colossal mountain carving that, when finished, will dwarf the four presidents.

The sculpture in progress is of the Lakota warrior Chief Crazy Horse astride a stallion with his arm and pointed hand stretched out over the horse's mane. It's taking awhile. The Crazy Horse Memorial — taller than the Washington Monument and well over two football fields wide — has been 64 years in the making. And problems in the underlying rock are now forcing the sculptors to deviate from the original model.

Sculptor Korczak Ziolkowski began the project 1948.

"He believed you can do anything in this world. Nothing is impossible as long as you're willing to work hard enough and pay the price," says the sculptor's wife, Ruth, who is now 86 years old.

Her long white hair is tied back, and despite her age, she still oversees all aspects of work on the monument. She and seven of her children took up the project after her husband's death in 1982. By the late 1990s, the face of Crazy Horse had emerged from the mountain carving. The last decade has been spent roughing out the horse's head — it's 22 stories high.

Today, mountain carving is high-tech. An engineer uses a laser measuring device to plot in a 3-D point on the side of the granite face. Rock is then removed — not using a hammer and chisel but with explosives.

For years the family followed their late father's model exactly. But Monique Ziolkowski, the sculptor's daughter, says the seams and cracks in the rock pose new challenges.

"He always said you had to work with Mother Nature because she'll beat you every time. So that's why we're working with the engineers, and we will be putting bolts in for support, but the bulk of the mountain needs to stand on its own," she says.

The changes include more rock left in place to support the outstretched arm and the horse's head. Teams of engineers and geologists carefully monitor each blast and help plot the way forward.

All this is paid for through private funding managed by a nonprofit organization. The project uses no tax dollars. Some critics have questioned the snail's pace of the progress. Matriarch Ruth Ziolkowski answers them by quoting her late husband.

"He said, 'Go slowly so you do it right.' And, I, for one, would like to have it go faster, but there are so many things that you have to do in order to do it right that it takes the time," she says.

This ambitious project has other critics, including some Native Americans who believe the humble Chief Crazy Horse would have never wanted his image carved into a sacred mountain. But supporters are quick to cite positive aspects of the memorial outside the carving, including the first classes held at a new on-site university, an expansive museum and a Native American college scholarship program targeting Native high school kids.

'It's A Lot of Rock'

On the main observation deck below the huge sculpture, a high school basketball team horses around. The team is from the Rosebud Reservation, and Coach Davis Reddest, a Lakota, brought his players here on a side trip from a nearby tournament. Reddest looks up at the giant carving, where construction excavators are removing recently blasted rock fragments.

"It's good. I just don't know if it's going to be completed in my lifetime," says Reddest. "It's going to be awhile. It's a lot of rock."

But others visiting this monument, including Bridget Martin from Wisconsin, are impressed with the progress. Martin remembers coming here as a kid back before the sculpture took shape.

"You kind of look forward to it for your kids to come back in 10 years or 20 years and see it finished," she says.

But the sculptors in the Black Hills won't estimate when the carving will be complete. It is now more than six decades in the making. In comparison, most historians say Egypt's Great Pyramid took about 20 years to finish.

South Dakota is famously home to Mount Rushmore. It's also home to a second colossal mountain carving that is 64 years in the making. When finished, the Crazy Horse Memorial will dwarf the four presidents. But problems in the underlying rock are now forcing its sculptors to deviate from the original model.

South Dakota public broadcasting's Charles Michael Ray has the story.

CHARLES MICHAEL RAY, BYLINE: If you're job is carving a mountain, you don't use a hammer and a chisel. You use this...

UNIDENTIFIED MAN: Fire in the hole. Fire in the hole. Fire in the hole.

(SOUNDBITE OF EXPLOSION)

RAY: A blast like this can remove over a thousand tons of rock at a time. The biggest mountain carving in the world is taller than the Washington Monument and well over two football fields wide. The sculpture in progress is of the Lakota warrior Chief Crazy Horse astride a stallion with his arm and pointed hand stretched out over the horse's mane. Sculptor Korczak Ziolkowski began the project 1948.

RUTH ZIOLKOWSKI: He believed that you can do anything in this world. Nothing is impossible as long as you're willing to work hard enough and pay the price.

RAY: The sculptor's wife, Ruth, is now 86 years old. Her long white hair is tied back, and despite her age, she still oversees all aspects of the work here. She and seven of her children took up the project after her husband's death in 1982. By the late '90s, the face of Crazy Horse emerged from the mountain carving. The last decade has been spent roughing out the horse's head. It's 22 stories high.

Today, mountain carving is high tech. Here, an engineer is using a laser measuring device to plot in a 3-D point on the side of the granite face. For years, the family followed their late father's model exactly. But Monique Ziolkowski, the sculptor's daughter, says seams and cracks in the rock pose new challenges.

MONIQUE ZIOLKOWSKI: He always said you had to work with Mother Nature because she'll beat you every time. And so that's why we're working with the engineers, and we will be putting bolts in for support, but the bulk of the mountain needs to stand on its own.

RAY: The changes include more rock left in place to support the outstretched arm and the horse's head. Teams of engineers and geologists carefully monitor each blast and help to plot the way forward. All of this is paid for through private funding managed by a nonprofit organization. The project uses no tax dollars. Some critics have questioned the snail's pace of the progress here. Matriarch Ruth Ziolkowski answers by quoting her late husband.

ZIOLKOWSKI: Well, he said, go slowly so you do it right. And, I, for one, would like to have it go faster, but there are so many things that you have to do in order to do it right that it takes the time.

RAY: This ambitious project has other critics, including some Native Americans who believe the humble Chief Crazy Horse would have never wanted his image carved into a sacred mountain. But supporters are quick to cite positive aspects of the memorial outside of the carving, including the first classes held at a new on-site university, an expansive museum and a Native American college scholarship program targeting Native high school kids like these...

This is a high school basketball team from the Rosebud Reservation. They're horsing around on the main observation deck below the huge sculpture of Crazy Horse. Coach Davis Reddest is Lakota. He brought his players here on side trip from a nearby tournament. Reddest looks up at the giant carving where construction excavators are removing recently blasted rock fragments.

DAVIS REDDEST: It's good. I just don't know if it's going to be completed in my lifetime. It's going to be a while. It's a lot of rock.

RAY: But others visiting this monument, including Bridget Martin from Wisconsin, are impressed with the progress. Martin remembers coming here as kid back before the sculpture took shape.

BRIDGET MARTIN: You kind of look forward to it for your kids to come back in 10 years or 20 years and see it finished.

RAY: But the sculptors in the Black Hills won't estimate when the carving will be complete. It's now more than six decades in the making. Compare that to Egypt's Great Pyramid, which most historians say took about 20 years to finish. This project could take another lifetime to complete, but its impact will likely extend long beyond that. For NPR News, I'm Charles Michael Ray in Rapid City, South Dakota. Transcript provided by NPR, Copyright National Public Radio.